Preventing stalling of carbureted



United States Patent 1 2,899,943 PREVENTING STALLING 0F CARBURETED INTERNAL COMBUSTION ENGINES This invention relates to the operation of carbureted internal combustion engines and more particularly to a novel method of preventing stalling thereof due to icing.

At temperatures ranging from about 30 to about 60 F. and at relatively high humidities, stalling of carbureted internal combustion engines has been encountered under idling or low load conditions. This is caused by the airborne moisture undergoing freezing due to the refrigerating effect encountered in normal fuel vaporization within the carburetor. The ice formed on the throttle plate and adjacent carburetor walls restricts the narrow air openings and causes engine stalling.

This problem is of increasing importance because of the design of newer automobiles. For example, present cars do not have a manual throttle and therefore the operator of the car is no longer able to increase the idle speed during the warm up period to prevent such stalling. Furthermore, the increasing use of automatic transmissions adds to this problem because the idle speed must be kept low to avoid creeping and, accordingly, the idle speed is not sufficiently fast to avoid stalling due to icing. Still another development which appears to add to this problem is the increased volatility of commercial gasolines, as it has been found that more frequent stalling is encountered with the more volatile fuels.

In accordance with the present invention, stalling due to icing in carbureted internal combustion engines is pre vented or at least considerably reduced by a novel method. It is understood that this method may be used in automotive, marine, stationary, airplane or other engines which utilize carburetors and which suffer because of icing in the carburetor.

In one embodiment the present invention relates to a method of preventing stalling due to icing of a carbureted internal combustion engine which comprises coating at least one member of the group of surfaces consisting of the throttle plate and adjacent internal surfaces of the carburetor with a gasoline resistant anti-nucleating hydrophobic material.

From the above embodiment it will be noted that the throttle plate and/or adjacent internal surfaces of the carburetor are coated with a particular coating material of critical composition. The coating material'must be gasoline resistant so that it will not be dissolved, destroyed or removed by the gasoline contacting the throttle plate and adjacent walls of the carburetor. Additionally, the coating material must be anti-nucleating, by which we mean that the coating material does not provide crystallization centers and induce crystallization on its surface; Furthermore, the coating material must be hydrophobic so that it is not wetted by water. The coating material may be thermoplastic but preferably is thermosetting.

Although a large number of coating materials are suitable for use in .the present invention and these may differ considerably in chemical type, they all have in commontheproperties of being gasoline resistant, anti nucleating and hydrophobic. They preventthe deposition and accumulation office on the carburetor surface. "Any ice particles which are formed will pass into the in-. take manifold and thence into the cylinders where they are dissipated witl r the products of combustion,

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As hereinbefore set forth, any suitable coating material meeting the requirements specified above may be employed in accordance with the present invention. A particularly preferred coating material is a silicone resin, a number of which are available commercially. The silicones are organo-polysiloxanes and consist of arrange ments of alternate silicon and oxygen atoms in which the silicon atoms are linked to organic groups, which are primarily alkyl groups (preferably methyl) or aryl groups (preferably phenyl), or the two types in combination. These polymers are heat stable, water repellent and chemically inert and thus are particularly suitable for use in the present invention.

While the silicones generally are preferred, other suitable coating materials may be used. Illustrative coating materials include the products formed by the chemical condensation of phenol-formaldehyde, phenol-fnrfural, urea formaldehyde, melamine formaldehyde, anilineformaldehyde, etc., polyvinyl chloride, polyvinylidene chloride, vinyl chloride-vinyl acetate copolymers, Teflon, polymerized monochlortrifluoroethylene, polyether (Epon) resins, polyvinylbutyral, polyesters such as those based on phthalic, maleic, or Carbic anhydride, and on various polyols as well as on allyl alcohol), polyethylene, polypropylene, methylmethacrylate and other acryloid polymers, polystyrene, styrene-butadiene copolymers, indene-coumarone copolymers, polymers of furfural and furfuryl alcohol, neoprene, butadiene-acrylonitrile copolymers, various rubber derivatives such as chlorinated rubber, cyclicized rubber, hard rubber, and the like; organic polysulfides of the Thiokol type; polyamides, for example nylon; various cellulose derivatives such as ethyl cellulose, cellulose acetate, cellulose acetatebutyrate, and cellulose nitrate, etc.

It is understood that the various coating materials which may be employed are not necessarily equivalent. However, all of them will be elfective in preventing or at least reducing stalling due to carburetor icing.

For maximum effectiveness it is preferable to apply the coating material to both the throttle plate and the adjacent walls of the carburetor. However, it is understood that benefits will be obtained by coating either the throttle plate or the adjacent inner surfaces of the carburetor. However, in accordance with the present invention, at least one and preferably both the throttle plate and the inner Walls of the carburetor are coated in the manner herein described. The coating may be applied in any suitable manner, as by spraying, dipping or brushing the throttle plate or carburetor surface with the coating material. Generally this is followed by baking, air-drying or other suitable treatment, depending upon the specific coating material used, to form a firm, hard, smooth coating of the desired characteristics. When the silicone resins are employed, the final treatment includes baking at a temperature of from about 150 to 1 about 350 C. for a period of from about 0.5 to 5 hours or more.

It is understood that the design of the carburetor and the thickness of the coating material will be correlated to permit ready operation of the carburetor in conventional manner. In general, a thin film of coating is suf ficient for normal use, although it is understood that the coating material may be applied in any desired thickness.

As will be shown in the following examples, a coated carburetor was used for an equivalent mileage of over 10,000 miles and the visual observation after such-use showed that the carburetor parts still were coated with the resin. However, when necessary, it is understood that the throttle plate and/or internal surfaces of the carburetor may again be given an additional treatment with the same or dilferent coating material j The following examples are introduced to illustrate further the novelty and utility of the present invention but not with the intention of unduly limiting the same.

EXAMPLE I The inner surfaces and throttle plate of a conventional automobile carburetor were coated with a silicone resin. The specific silicone resin used is available in the open market as Dow-Corning DC-803. This resin bakes to a hard but brittle finish; to provide greater flexibility, 20% by volume of Dow-Corning DO-802. silicone resin was blended therewith. The silicone resin blend was applied by brushing to both the throttle plate and internal walls of a Chevrolet carburetor to give a coating of about 0.003 thickness, following which the carburetor was placed in an oven and the coating material wasbaked at 200 C. for 2.5 hours.

The carburetor coated in the above manner was evaluated in two separate engines. It first was adapted for use in a 1952 Oldsmobile engine and run for a period equivalent to a mileage of about 2,000 miles. The carburetor then was removed from the Oldsmobile engine and evaluated in a Chevrolet engine which was arranged to induce icing conditions. In this arrangement the air was passed through ice cubes in order to saturate the air with water vapor at 32 F. and then the air was supplied through an insulated line to the carbureter. The evaluation in the Chevrolet engine ran for about one hour and then the carburetor was removed from the Chevrolet engine and replaced in the Oldsmobile engine. This cycle was repeated to a running time of 196.5 hours which is equivalent to a mileage of 10,600 miles. The purpose of the evaluation in the Oldsmobile engine was to determine the life of the coating during continuous contact with gasoline under normal use. After the equivalent of 10,600 miles operation, the carburetor was removed and visually inspected. There appeared to be no measurable wearing effect of the gasoline on the coating material.

In the Chevrolet engine the icing effect was determined by the extent of throttle advance necessary to maintain a given speed of 1600 r.p.m. Since icing restricts the flow through the carburetor, it is apparent that it is necessary to increase the throttle opening to offset the effect of icing in order to maintain a constant speed. Comparable tests also were conducted using a duplicate carburetor which had not been coated in the manner described above. Also, comparable runs were made in which 1% by weight of isopropanol was incorporated Y in the gasoline. Isopropanol is being used in gasoline to prevent icing and the results are interesting for comparative purposes. The results of these tests are reported in the following table:

From the data in the above table, it is seen that the silicone coated carburetor was very effective because it did not require any increase in the throttle opening in order to maintain the constant speed. It is apparent that this method is exceedingly more effective than the use of isopropanol.

EXAMPLE II The ice collected in the carburetor during the runs described in Example I was melted, collected and the amount measured. These results are reported in the following table:

Table 11 Description Ml. of H20 Uncoated carburetor 0. 5 Gasoline containing 1% isopropanol and uncoated carburetor, V 0.42 Silicone coated carburetor--." 0. 05

EXAMPLE III Another set of runs was made in the Chevrolet engine described in Example I. However, in this test a synthetic gasoline mixture comprising 50% by volume of toluene and 50% by volume of isopentane was employed be! cause this mixture provides extreme icing conditions. When evaluated in the same manner as described in Example I, the run using an uncoated carburetor required a throttle advance of 0.073" in the interval be tween the first and fifth minutes, while the silicone coated carburetor required an advance of only 0.01 in the same interval. Here again it will be noted that the silicone coated carbureter was effective in reducing the throttle opening requirements to maintain constant speed.

We claim as our invention:

1. The method of preventing stalling due to icing o a carbureted internal combustion engine which comprises coating at least one member of the group of surfaces consisting of the throttle plate and adjacent internal surfaces of the carburetor with a gasoline resistant anti? nucleating hydrophobic material.

2. The method of preventing stalling due to icing of a carbureted internal combustion engine which comprises coating the carburetor throttle plate with a gasoline resistant anti-nucleating hydrophobic material.

3. The method of preventing stalling due to icing of a carbureted internal combustion engine which comprises coating the internal surfaces of the carburetor adjacent to the throttle plate with a gasoline resistant anti-nucleating hydrophobic material.

4. The method of preventing stalling due to icing of a carbureted internal combustion engine which comprises coating the throttle plate of the carburetor with a silicone resin, and subsequently baking the same to form a firm, hard, smooth coating.

5. The method of operating a carbureted internal combustion engine without stalling otherwise encountered under relatively high humidity conditions which comprises effecting the operation thereof with a carburetor having at least one member of the group of surfaces con.- sisting of the throttle plate and adjacent surfaces coated witlgla gasoline resistant anti-nucleating hydrophobic materi 6. The method of operating a carbureted internal combustion engine without stalling otherwise encountered under relatively high humidity conditions which comprises effecting the operation thereof with a carburetor in which the throttle platethereof has been coated with a silicone resin.

7. A carburetor having at least one member of th group of surfaces consisting of the throttle plate and adjacent internal surfaces coated with a gasoline resistant anti-nucleating hydrophobic material.

8. A carburetor having the throttle plate thereof coated with a silicone resin.

No references cited. 

